Radio receiver



July 6, 1937. R, 5 HOLMES 2,086,331

RADIO RECEIVER Filed Jan. 27, 1934 Patented July 6, 1937 PATENT OFFICE RADIO RECEIVER Ralph S. Holmes, Hadclonfield, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application January 27, 1934, Serial No. 708,547

6 Claims.

My invention relates to radio receiving apparatus, and particularly to apparatus designed for the reception of signals at ultra high frequencies such as those utilized in television transmission and reception.

In a receiver employed for receiving signals having a frequency of the order of 40 megacycles, for example, difficulty is experienced in providing circuit connections short enough for satisfactory in operation of the receiver. It has also been found difficult to prevent physical changes in the spacing between the various receiver parts such as the condensers, coils, and tube sockets. If such changes in spacing do occur, the operation of the receiver is unsatisfactory, especially in the case of a superheterodyne receiver.

In a superheterodyne receiver, the principal difficulty is in preventing undesired variations in the frequency of the local oscillator, and to prevent such variations the spacing between receiver parts must remain constant. It is also important that the oscillator connections be short for preventing variations in the oscillator frequency during the reception of a signal.

It is, accordingly, an object of my invention to provide an improved high frequency radio receiver.

It is further an object of my invention to provide an improved receiver of the superheterodyne type.

It is a still further object of my invention to provide a receiver of the superheterodyne type in which the local oscillator will generate ultrahigh frequency oscillations having a constant frequency.

In one embodiment of my invention I utilize a gang condenser which consists of a plurality of variable condenser units mounted in a single frame. The oscillator inductor and certain radio frequency inductance coils are mounted upon this condenser frame. Also, the oscillator electric discharge tube is supported from a bracket fastened to the condenser frame, the electrode terminals of the tube being positioned as close as possible to the oscillator condensers and coils.

Other objects, features, and advantages of my invent-ion will appear from the following description taken in connection with the accompanying drawing in which Figure 1 is an end view of one embodiment of my invention;

Fig. 2 is a plan view of the apparatus shown in Fig. 1 with a portion broken away;

Fig. 3 is a view of the under, side of the portion broken away in Fig. 2;"

Fig. 4 is a view taken on line 44 of Fig. 2 and Fig. 5 is a circuit diagram of the apparatus shown in the preceding figures.

Referring to the drawing, the apparatus comprises a gang condenser which, in the embodiment illustrated, consists of three variable capacity units or condensers I, 3 and 5 mounted upon a common metallic frame I. The frame consists of a back plate 9 and end plates II and i3 integral therewith and bent at right angles thereto. The frame 1 is rigidly braced by means of a bottom plate l5, each end of which is fas toned to an end plate in any suitable manner as by welding.

The frame is also braced at the top by means of a metal plate H which is welded or otherwise suitably fastened at each end to the end plates, this plate also functioning as a condenser plate common to three trimmer condensers l9, 2! and 23 as will be more fully explained hereinafter.

Each variable capacity unit is of a conventional construction and consists of a plurality of spaced stator plates and a plurality of rotor plates wl'iich may be rotated to interleave therewith. The construction will be understood by referring to Fig. i where the stator plates 25 of condenser E! are shown mounted upon the condenser frame I and insulated therefrom by means of plates 21 and 29 of insulating material. The lower plate 2?, which is riveted or otherwise suitably fastened to the lower edge of the back plate 9 of the condenser frame, extends inside the condenser frame whereby the lower edge of the stator plates 25 may be bolted thereto. Likewise, the upper plate 29 is fastened to the upper edge of the back plate 9 whereby the upper edge of the stator plates 25 may be bolted or otherwise fastened thereto.

The rotor plates of the condensers l, 3 and 5 are mounted upon a common shaft 3l which is journaled in the end plates II and I3 of the condenser frame. Thus all of the condenser rotor plates are electrically connected to the frame 1, while the three groups of stator plates are insulated from the condenser frame and from each other.

Each variable capacity unit is provided with one of the above-mentioned trimmer condensers, the three trimmer condensers being identical in construction. Their construction will be understood by referring to Fig. 4 where trimmer condenser is shown to consist of a fixed condenser plate which is the above mentioned portion ll of the condenser frame, an adjustable condenser plate 33, and a strip 35 of insulating material,

such as mica, positioned between the two plates. One end of the adjustable condenser plate 33 is fastened to the insulating plate 29 and electrically connected to the stator plates by means of the bolt 3! or other fastener which supports the stator plates.

The capacity of the trimmer condenser I9 may be adjusted by means of a bolt 39 and nut 4| positioned at the free end of the adjustable condenser plate 33 so that a Washer 43 of insulating material may be forced against said free end.

A pair of radio frequency transformer coils 45 and 4'! and an oscillator coil 49 are mounted upon a rod 5| of insulating material fastened at each end to cars 53 and 55 extending upwardly from the end plates I I and I3, respectively, of the condenser frame. Each coil consists of a few turns of wire wound upon a cylindrical tube.

A socket 5? for an electric discharge tube is supported from a bracket 59 fastened to the back plate 9 of the condenser frame. The socket 51 is so positioned that the terminals G, P and C for the grid, plate and cathode, respectively, are as close as possible to the inductance coils and condensers to which they are connected.

In particular, the grid terminal G of the socket is placed close to the oscillator coil 49.

While the tube socket 51 may be of any suitable design, it has been illustrated with terminals consisting of a plurality of contact elements 6| for the tube prongs 63, each contact element having a back-up spring for insuring good contact between the contact element and the tube F prong.

The electrical connections of the above described apparatus will now be described in connection with Fig. 5. The primary winding 45 of the radio frequency transformer has the variable condenser i connected thereacross to form a tunable primary circuit, the connection between one end of the coil and the rotor plates of condenser i being through a lead 51 and the condenser frame I. The connection from the other end of the coil 45 to the stator plates of the condenser l is through a tab 89 which extends from the adjustable plate 33 of the trimmer condenser 19 and through the bolt 37. The trimmer condenser |9, obviously, is connected across the variable condenser I.

The incoming signal preferably is impressed upon the tuned primary circuit of the radio frequency transformer through a small coupling condenser ll formed by 2. lug 13 which is bolted to an arm I5 extending from the adjustable capacity plate 33 and which is insulated therefrom by washers 11. It will be understood that since the receiver is designed to be used for the reception of very high frequency signals the coupling capacity may be very small. Ordinarily, the circuit for the incoming signal will be completed by grounding the condenser frame.

The secondary winding 4? of the radio frequency transformer is shunted by the variable condenser 3, one end of the coil 41 being connected to a tab 19 extending from the adjustable plate of the trimmer condenser 2|, while the other end is connected through a lead 8| to the condenser frame I and from the frame I to the rotor of the condenser 3. The trimmer condenser 2i is connected across the condenser 3 in the manner shown in Fig. 4.

The plate of the trimmer condenser 2| is provided with an upwardly extending tab 83 to which the grid of the first detector 85 may be connected.

The oscillator coil 49 consists of two sections 499, and 4%, section 499, being tunable by means of the variable condenser 5, and the section 49b acting as a feed-back coil to produce sustained oscillations.

As will be noted from the circuit diagram, the variable condenser 5 is connected in series with an adjustable condenser 81, the two condensers being connected across the coil section 49a. Referring to Figs. 1 and 2, the adjustable capacity 81 consists of a condenser plate 89 which is connected to the condenser frame "I, and an adjustable plate 9| which is supported at the upper end by means of a small rectangular plate 93 of insulating material. The plate 93 is in turn supported from the ear 55 of the end plate I3. The condenser plates 89 and 9| are insulated from each other in the usual manner by means of a mica plate 95. It will be noted that the adjustable plate 9I is insulated from the condenser frame I. In actual practice, the condenser 89 consists of more than two plates, alternate plates being connected together to increase the capacity. To avoid complicating the drawing, this specific structure has not been illustrated.

In order to permit a short and rigid connection between the oscillator coil 49 and the condenser plate 9|, an opening 91 is provided in the upper part of the end plate I3 and the car 55.

This connection is from the tapped point on the oscillator coil 49 to the adjustable plate 9| of the condenser 81 through a lead 99 which is soldered to a tab IOI extending through the opening 91. The plate 89 of the condenser 81' is connected to the rotor of the variable condenser 5 through the condenser frame I. The end of the coil 49 which is the farther away from the coil 41 is connected to the stator of the variable condenser 5 through a lead I03 which is soldered to a tab I05 extending from the adjustable plate of trimmer condenser 23. Like the other variable condensers I and 3, the condenser 5 is shunted by a trimmer condenser which is indicated at 23.

The control grid I01 of the oscillator tube I09 is connected to the tunable oscillator circuit through a small coupling condenser I I I, one terminal of the condenser being soldered to the tab I05 and the other terminal being soldered to the grid terminal G of the socket 51. The cathode terminal C of the socket 5'! is connected to the condenser frame I whereby the input circuit of the tube I09 is connected across the tunable oscillator circuit. A grid leak resistor I I3 is connected between the grid terminal G of the socket and the condenser frame I.

A suitable operating potential is applied to the a plate II5 of the oscillator tube I89 through a radio frequency choke coil III which is connected through a lead I E4 to the tapped point on the oscillator coil 49 and through the feed-back n portion 49b of the coil 19, the end of coil 49 closest to coil 4'! being connected to plate 5 through a lead II9. From the foregoing description it will be evident that I have provided a frequency converting unit having parts which are rigidly mounted with respect to each other and having leads which are short and rigid whereby steady high frequency oscillations may be maintained. In the reception of high frequency signals, this is very important as otherwise there will be distortion and apparent fading of the signal during reception.

Various modifications may be made in my invention without departing from the spirit and scope thereof, and I desire, therefore, that only such limitations shall be placed thereon as are necessitated by the prior art and are set forth in the appended claims.

I claim as my invention:

1. In a superheterodyne receiver, a condenser comprising a frame having stator and rotor plates mounted thereon to form a plurality of variable capacity units, a plurality of inductance coils mounted upon said frame, one of said coils being connected to one of said capacity units to form a tunable selecting circuit, a first detector coupled to said selecting circuit, another of said coils being connected to another of said capacity units to form a tunable oscillator circuit, said two circuits being electrically coupled, means for maintaining sustained oscillations in said oscillator circuit, said means including an electric discharge device, and means for mounting said discharge device upon said condenser frame.

2. In a radio receiver for the reception of short Wave signals, a gang condenser consisting of a frame having stator and rotor plates mounted thereon to form one condenser unit and having other stator and rotor plates mounted thereon to form at least one other condenser unit, a detector tube, a selector circuit which includes one of said condenser units and a coil mounted on said frame, said selector circuit being connected to supply received signals to said detector tube, an oscillator coupled to said detector tube, said oscillator comprising an oscillator tube and a tunable circuit, said tunable circuit including another of said condenser units and a coil mounted on said frame, and means for mounting said oscillator tube upon said condenser frame.

3. In a superheterodyne receiver, a gang condenser comprising a frame and a plurality of condenser units, an oscillator tunable over a predetermined frequency range, said oscillator comprising one of said condenser units, an inductance coil mounted upon said frame and connected across said one condenser unit to form a tunable circuit, and an electric discharge tube mounted upon said frame and so coupled to said tuned circult as to produce oscillations, a radio frequency selecting circuit tunable over a predetermined frequency range, said selecting circuit comprising another of said condenser units and another inductance coil mounted upon said frame, and a first detector coupled to said selecting circuit, said oscillator also being coupled to said first detector.

1. In a superheterodyne receiver a gang condenser consisting of a metallic frame having stator plates and rotor plates mounted thereon to form a plurality of condenser units, said rotor plates being on a rotor shaft and being conductively connected to said frame, a detector, a plurality of inductance coils mounted on said frame, one of said coils having one end connected to said frame and having the other end connected to the stator of one of said condenser units, another of said coils having one end connected to said frame and having the other end connected to the stator of another of said condenser units, said firstmentioned and second-mentioned coils being so coupled and tuned as to function as a radio frequency selecting circuit, said first-mentioned coil being adapted to have signals impressed thereon and said second-mentioned coil being coupled to said detector, an oscillator tube mounted on said frame, another of said coils being connected across another of said condenser units to form a tunable oscillator circuit and means for so coupling said oscillating circuit and said oscillator tube as to produce a source of oscillations, said second mentioned and third-mentioned coils being inductively coupled whereby a signal impressed upon said first-mentioned coil is mixed with said oscillations in said detector to produce an intermediate frequency signal.

5. The invention according to claim 4 characterized in that said condenser units and said coils are located along the axis of the rotor shaft of said condenser in the order named.

6. In a superheterodyne receiver, a gang condenser consisting of a metallic frame having stator and rotor plates mounted thereon to form a plurality of condenser units, said rotors being conductively connected to said frame, a detector, a plurality of inductance coils mounted on said frame, one of said coils having one end connected to said frame and having the other end connected to the stator of one of said condenser units, another of said coils having one end connected to said frame and having the other end connected to the stator of another of said condenser units, said first-mentioned and second-mentioned coils being so coupled and tuned as to function as a radio frequency selecting circuit, said first men tioned coil being adapted to have signals impressed thereon and said second-mentioned coil being coupled to said detector, an oscillator tube mounted on said frame, a series condenser mounted on said frame, said series condenser having one plate conductively connected to said frame and having the other plate insulated therefrom, another of said coils being connected at one point to the stator of another of said condenser units and being connected at another point to the insulated plate of said series condenser to form an oscillatory circuit, and means for so coupling said oscillatory circuit and said oscillator tube as to produce a source of oscillations, said second-mentioned and third-mentioned coils being inductively coupled whereby a signal impressed upon said first-mentioned coil is mixed with said oscillations in said detector to produce an intermediate frequency signal.

RALPH S. HOLMES. 

